If you could have lived in North America or Europe twenty thousand years ago, you would have believed you were at the North Pole. Most of the Earth was covered by a thick layer of ice and snow.
Many animals that lived there’ they were like the animals that live in cold places today. There were bears, elk and wolf packs. There were also some animals that looked like huge elephants, but their bodies were covered with hair. These animals are called mammoths, word that means very big.
Mammoths, dinosaurs and other ancient animals have disappeared. Over the years, many of these animals died and others changed shape. All the animals are still changing shape. In a million years, the world will be as different from today as it was a million years ago. Many of today's animals will have disappeared. There may be new kinds of animals. The history of life on Earth is one that is always changing.
